Question

Right now, I’m using mongodump and bsondump to get documents out of MongoDB, then applying regexes to the documents to get the value I want. What I really want is just a flat file of, say, the email address of every user in the users collection, in a flat file that I can then manipulate with grep, uniq, etc.

In MySQL, it’d be:

mysql < query.sql > outfile.txt

The query.sql file would be something like:

SELECT email FROM users;

But in Mongo, when I pass a .js file in, I’m still not sure how to make it output single values.

mongo --db test < query.js > outfile.txt

What would query.js be for the users collection?

Answer 1

You could use forEach to run each result through a JavaScript function and print a line in the format you want:

db.users.find().forEach(function(user) {
    print(user.email);
});

The --quiet command line option is also useful for removing the header lines from the output.